1. Field of the Invention
The invention relates to a crystal growth furnace, more particularly to a heating electrode assembly for a crystal growth furnace.
2. Description of the Related Art
As shown in FIG. 1, Taiwanese Patent No. 1346152 discloses a conventional crystal growth furnace 1 that includes: an upper furnace wall 11, a bottom cover 12 for closing a bottom part of the upper furnace wall 11, a heat insulation unit 13 disposed in the upper furnace wall 11 and the bottom cover 12, a load board 14 disposed in the heat insulation unit 13, a plurality of electrode units 15, and a plurality of resistive graphite heaters 16. Each of the electrode units 15 has a metal electrode column 151 fixed on the upper furnace wall 11 and a graphite electrode column 152 that extends downwardly from the metal electrode column 151 through the heat insulation unit 13. The graphite electrode column 152 of each of the electrode units 15 has a bottom portion connected to a respective one of the graphite heaters 16.
When growing a polycrystalline silicon crystal, a silicon raw material (not shown in the Figure) is placed in a crucible 17 on the load board 14. Then, a high-current low-voltage electric power is provided to the metal electrode columns 151 through a plurality of cables 18 (only one cable is shown in FIG. 1) which are externally connected to the conventional crystal growth furnace 1, so that large currents flow in sequence from the metal electrode columns 151 through the graphite electrode columns 152 to the graphite heaters 16, generating a thermal field within the heat insulation unit 13 so as to melt the silicon raw material in the crucible 17 into a molten silicon 19.
However, it should be noted herein that, since the heat insulation unit 13 is generally made of conductive material, such as graphite, carbon fiber, etc., and in the conventional crystal growth furnace 1 there is no electrical insulation between the graphite electrode columns 152 of each of the electrode units 15 and the heat insulating unit 13, electrical arcs may be formed between the graphite electrode columns 152 and the heat insulation unit 13 under large currents. Such electrical arcs can cause damage to the heat insulation unit 13. Therefore, when the conventional crystal growth furnace 1 has been in use for a long period of time, the burning of the heat insulation unit 13 by the electrical arcs will inevitably result in variation of the thermal field within the conventional crystal growth furnace 1, and will adversely affect the quality of a grown crystal.
Referring to FIG. 2, China Patent Publication No. CN202107794U discloses a conventional polycrystalline crystal growth furnace 2 that comprises: a furnace 21, a heat insulation cage 22 disposed in the furnace 21, a heat insulation top plate 23 disposed at a top portion of the heat insulation cage 22, a plurality of electrode units 24 extending through the heat insulation top plate 23, and a heater 25 connected to the electrode units 24. However, there is not shown any design of electrical isolation between each of the electrode units 24 and the heat insulation top plate 23 of the conventional polycrystalline crystal growth furnace 2. Therefore, similar to the conventional crystal growth furnace 1, the conventional polycrystalline crystal growth furnace 2 also suffers from the burning problem of the heat insulation top plate 23 which is caused by the electrical arcs, and which results in variation of the thermal field within the conventional crystal growth furnace 2, so as to adversely affect the quality of the grown crystal.
From the foregoing, it is evident that improvement on the structure of the heating electrode assembly, which may ameliorate the burning problem of the heat insulation boards and improve the quality of grown crystal, is highly desired in this technical field.